A typical apparatus for dispensing a heated liquid, such as hot melt adhesive, generally includes a dispensing gun or module having a valve element that opens and closes a dispensing outlet. The valve element is positioned within a passage supplied with pressurized liquid and contacts a valve seat to prevent the heated liquid from flowing to the outlet. To dispense the heated liquid, an actuator, such as an electrically and/or pneumatically operated actuator, causes the valve element to move away from the valve seat and allows the heated liquid to flow from the passage to the outlet. A biasing mechanism, such as a spring, or the same actuator may then cause the valve element to move back toward the valve seat to close the outlet.
The dispensing module typically receives the heated liquid from a liquid supply component, such as a manifold. For example, a manifold may be coupled to both a source of the liquid adhesive and an inlet of the dispensing module. The heated liquid flows through various internal passageways within the manifold before reaching the inlet of the dispensing module. Because the dispensing module and manifold are separate components, they must typically be coupled together in a secure manner to prevent leakage.
One method for coupling the dispensing module to the manifold uses conventional fasteners. For example, one or more screws may be inserted through the dispensing module to engage threaded holes tapped into the manifold. The screws are tightened (i.e., placed in tension) until the dispensing module is pressed against the manifold with sufficient force to maintain a seal between an outlet of the manifold and the inlet of the dispensing module.
In some liquid dispensers, several factors can make the use of screws and other conventional fasteners challenging. For example, a heater within the manifold typically creates an environment of relatively high temperatures. The forces required to effectively couple the dispensing module to the manifold may exceed the pullout strength of the screws at such relatively high temperatures. As a result, tightening the screws to secure the dispensing module may lead to failure of the screw threads, failure of the threads in the tapped hole of the manifold, or both.
Another factor that can make the use of screws and other conventional fasteners challenging relates to the space required to accommodate the screws. Both the dispensing module and manifold include internal passages for the heated liquid that should be avoided by the screws. Because of the limited space available for the screws, the size of the screws themselves is typically limited. Smaller screws have lower resistance to failure than larger screws. As a result, a greater number of smaller screws may be required to press the dispensing module against the manifold with the same amount of force that would be applied if larger screws were used. Finding the space to accommodate more screws can be difficult due to the space limitations discussed above.
Moreover, in some liquid dispensers, the manifold further includes a piston or piston assembly that actuates a pivot arm connected the valve element within the dispensing module. Examples of such heated liquid dispensers assigned to the assignee of the present invention are described in U.S. Patent Application Publication Nos. 2005/0236438 and 2006/0097010 and U.S. Provisional Patent Application Serial No. 60/865,886, the disclosures of which are fully incorporated herein by reference. The additional passages needed to accommodate the piston and pivot arm, along with the relatively small thicknesses associated with these dispensers, may make it even more difficult to accommodate screws or other conventional fasteners.
Therefore, new devices and methods for coupling a dispensing module to a liquid supply component, such as a manifold, are highly desirable.